JP4977929B2 - Method for forming a microlens - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of forming the luma microlenses put like the solid-state imaging device.
[0002]
[Prior art]
A solid-state imaging device includes a large number of photoelectric conversion elements arranged in a matrix on a semiconductor substrate, and a microlens that collects incident light on the photoelectric conversion elements is arranged in front of each photoelectric conversion element for each photoelectric conversion element. Has been. This microlens is formed by processes such as patterning a photoresist layer, forming a microlens pattern for transfer, and transferring the pattern to a resin layer.
[0003]
6 is a partial plan view showing a mask for forming a conventional microlens for a solid-state imaging device, FIG. 7 is a partial plan view showing a photoresist pattern in a conventional microlens formation process, and FIG. 8 is a conventional microlens. FIG.
In forming the microlens, first, a resin layer is formed on a photoelectric conversion element arranged on a semiconductor substrate via a color filter, and a photoresist layer is formed thereon. Then, the photoresist layer is patterned by photolithography using a mask 102 as shown in FIG. In this mask 102, a large number of rectangular mask patterns 104 corresponding to the respective microlenses in a plan view are arranged close to each other in a matrix, and as a result, the photoresist layer has a matrix shape as shown in FIG. Are patterned into a plurality of photoresist patterns 106 having a substantially rectangular shape in plan view, which are arranged close to each other.
[0004]
Thereafter, the photoresist pattern 106 is converted into a convex microlens pattern for transfer by heat melting, and then the transfer microlens pattern and the resin layer are etched to make the solid shape of the transfer microlens pattern a resin. As shown in FIG. 8, a large number of microlenses 108 having a substantially rectangular shape in a plan view and arranged close to each other are formed.
[0005]
[Problems to be solved by the invention]
However, in such a conventional method for forming the microlens 108, due to insufficient resolution when patterning the photoresist layer, etching is performed at the corners of the mask pattern 104 that should not be etched, so that the photoresist pattern 106 is formed. Will have a shape with corners of each corner 110 removed. Therefore, as shown in FIG. 8, the formed microlens 108 similarly has a corner portion 112 with a rounded shape, the area of the microlens 108 is reduced, and the non-condensing region 114 is enlarged. The light incident on the non-condensing region is not guided to the photoelectric conversion element, resulting in a decrease in the sensitivity of the solid-state imaging element.
[0006]
The present invention has been made to solve such problems, and an object of the present invention is to provide a method of forming a microlens that can reduce or eliminate the non-light-condensing region.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a method for forming a microlens according to the present invention comprises forming a resin layer of a synthetic resin for forming a microlens on a substrate, forming a photoresist layer on the resin layer, and forming a photoresist. A mask having a sub-island pattern in which each mask pattern corresponding to each pattern extends outward from each position corresponding to each rectangular corner of the photoresist pattern and has a right-angled corner on the diagonal of the mask pattern, A large number of rectangular photoresist patterns in plan view that are placed on the photoresist layer and patterned by photolithography using the mask so as to be close to each other at a predetermined distance in a matrix. And forming a convex microlens pattern for transfer by thermally melting the photoresist pattern. Forming a over emissions, by transferring the three-dimensional shape of the transfer microlens pattern the entire surface by dry etching of the transfer microlens pattern and the resin layer on the resin layer, wherein the predetermined distance is transferred to the resin layer as zero to shorten, to form a plurality of rectangular shape in plan view of the micro lens unit side adjacent to each other are arranged in a matrix in contact.
[0008]
Thus, in the microlens formation method of the present invention, each mask pattern corresponding to the transfer photoresist pattern is a mask provided with the sub-island pattern as a mask used for forming the transfer photoresist pattern, and The sub-island pattern corrects that each corner of the photoresist pattern has a rounded shape due to insufficient resolution when patterning the photoresist layer, and uses the corrected photoresist pattern to transfer micro-patterns for transfer. The solid shape of the microlens pattern for transfer is transferred to the resin layer by dry-etching the entire surface of the lens pattern and the resin layer, and a predetermined distance between adjacent sides of the microlens unit formed by transferring to the resin layer. It acts to shorten the distance to zero . As a result, by correctly forming each photoresist pattern in a rectangular shape in plan view, it is possible to arrange a plurality of rectangular microlens units in plan view in contact with each other adjacent to each other in a matrix, and to form a non-condensing region. It can be reduced or eliminated.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a partial plan view showing a mask used in an example of a microlens forming method according to the present invention. FIGS. 2A to 2D are views of a microlens based on a microlens forming method according to an embodiment. It is a fragmentary sectional side view which shows each formation process. 3 is a partial plan view showing a photoresist pattern formed by the microlens forming method of the embodiment, and FIG. 4 is a portion showing the microlens formed by the microlens forming method of the embodiment. It is a top view.
[0010]
Here, as an example, a microlens of a CCD (Charge Coupled Device) solid-state imaging device is formed, and a microlens is formed on the color filter layer 2 shown in FIG. The color filter layer 2 is formed on a planarizing film 4 made of, for example, plasma nitride, and is omitted in the drawing, but a number of layers are formed on a semiconductor substrate made of silicon under the planarizing film 4. Photoelectric conversion elements (not shown) are arranged in a matrix with electrodes and the like, and an oblique light film and the like are formed on the photoelectric conversion elements at portions other than the light receiving portion. The microlens is arranged for each photoelectric conversion element so as to collect incident light for each photoelectric conversion element.
[0011]
First, as shown in FIG. 2A, a transparent resin layer 8 made of a synthetic resin for forming a microlens 6 is formed on a semiconductor substrate. Subsequently, as shown in FIG. 2B, a photoresist layer 10 is formed on the resin layer 8, the photoresist layer is patterned by photolithography, and as shown in FIG. A large number of rectangular photoresist patterns 12 arranged in a matrix in a rectangular shape in plan view are formed.
[0012]
Here, as a mask used when patterning the photoresist layer 10 by photolithography, as shown in FIG. 1, each mask pattern 16 corresponding to each of the photoresist patterns 12 having a rectangular shape in plan view has each corner. A mask 14 having a sub-island pattern 20 extending outward in a diagonal direction is used as the portion 18.
[0013]
Next, as shown in FIG. 2B, the photoresist pattern 12 is thermally melted to form a convex transfer microlens pattern 22.
Thereafter, the entire surface of the transfer microlens pattern 22 and the resin layer 8 is dry-etched, and the three-dimensional shape of the transfer microlens pattern 22 is transferred to the resin layer 8, as shown in FIGS. 2C and 4. In this way, a large number of microlenses 6 having a rectangular shape in plan view arranged close to each other are formed.
[0014]
As described above, in the microlens forming method of the present embodiment, each mask pattern 16 corresponding to the transfer photoresist pattern is used as the mask for use in forming the transfer photoresist pattern as described above. The sub-island pattern 20 has a shape in which each corner 12A of the photoresist pattern 12 has a rounded corner as in the prior art due to insufficient resolution when patterning the photoresist layer 10. It acts to correct that.
[0015]
As a result, as shown in FIG. 3, each photoresist pattern 12 can be correctly formed in a rectangular shape in plan view, and the arrangement of the microlenses 6 shown in FIG. 4 is compared with FIG. 8 in the conventional case. As can be seen, the non-light-condensing region 24 can be reduced. Therefore, the amount of light incident on each photoelectric conversion element of the solid-state image sensor increases, and the sensitivity of the solid-state image sensor improves.
[0016]
In addition, by further appropriately performing dry etching from the state of FIG. 2C, as shown in FIG. 2D, each microlens 6 including the non-light-condensing region 24 (FIG. 4) is included. It is also possible to eliminate the non-light-condensing region in the peripheral part.
Such dry etching can be performed with a reactive ion etching apparatus (RIE apparatus) using CF ₄ (carbon tetrafluoride) or a mixed gas of oxygen and CF ₄ as a process gas. .
FIG. 5A is a partial plan view showing the microlens 6 formed by the microlens forming method of the embodiment when the non-light-condensing region around the microlens is eliminated by further dry etching. (B) is a partial top view which shows the micro lens 108 by the formation method of the conventional micro lens. In the conventional method, the non-condensing region 114 is reduced but not eliminated. However, in the present embodiment, the non-condensing region around the microlens including the non-condensing region 24 is eliminated. be able to.
[0017]
In this embodiment, the case of a CCD solid-state image sensor has been described as an example. However, the present invention is naturally effective for a MOS solid-state image sensor, and further, for each liquid crystal cell of a liquid crystal display device. It is also effective for the microlenses to be formed.
Further, in the case where an in-layer lens is formed on the color filter layer 2 that is convex downward and the upper surface is flat, and further an upward convex micro lens is formed thereon, the micro lens is also formed. The present invention can be applied in stages.
[0018]
【Effect of the invention】
As described above, in the method for forming a microlens of the present invention, as a mask used for forming a transfer photoresist pattern, each mask pattern corresponding to the transfer photoresist pattern uses a mask provided with the sub-island pattern. The sub-island pattern acts to correct the corners of the photoresist pattern to have a corner shape due to insufficient resolution when patterning the photoresist layer. As a result, each photoresist pattern can be correctly formed in a rectangular shape in plan view, and the non-light-condensing region can be reduced or eliminated.
Therefore, for example, in the case of a solid-state image sensor, the amount of light incident on each photoelectric conversion element increases, and the sensitivity of the solid-state image sensor can be increased.
[Brief description of the drawings]
FIG. 1 is a partial plan view showing a mask used in an example of a method for forming a microlens according to the present invention.
FIGS. 2A to 2D are partial cross-sectional side views showing respective steps of forming a microlens based on the microlens forming method of the embodiment. FIGS.
FIG. 3 is a partial plan view showing a photoresist pattern formed by the microlens forming method of the embodiment.
FIG. 4 is a partial plan view showing a microlens formed by the microlens forming method of the embodiment.
FIG. 5A is a partial plan view showing a microlens formed by the microlens forming method of the embodiment when the non-condensing region around the microlens is eliminated by further dry etching. (B) is a partial top view which shows the micro lens by the formation method of the conventional micro lens.
FIG. 6 is a partial plan view showing a mask for forming a conventional microlens for a solid-state imaging device.
FIG. 7 is a partial plan view showing a photoresist pattern in a conventional microlens formation process.
FIG. 8 is a partial plan view showing a conventional microlens.
[Explanation of symbols]
2 ... Color filter layer, 4 ... Planarization film, 6 ... Microlens, 8 ... Resin layer, 10 ... Photoresist layer, 12 ... Photoresist pattern, 14 ... Mask, 16 ... Mask pattern , 18 ... corner, 20 ... sub-island pattern, 22 ... microlens pattern for transfer, 24 ... non-condensing region, 102 ... mask, 104 ... mask pattern, 106 ... photoresist pattern, 108 …… Microlens, 110 …… Corner, 112 …… Corner, 114 …… Non-condensing area.

Claims (6)

A resin layer made of synthetic resin for forming a microlens is formed on the substrate,
Forming a photoresist layer on the resin layer;
A mask having a sub-island pattern in which each mask pattern corresponding to each of the photoresist patterns extends outward from each position corresponding to each corner of the photoresist pattern rectangle and has a right-angled corner on the diagonal of the mask pattern On the photoresist layer,
Using the mask, the photoresist layer is patterned by photolithography to form a large number of rectangular photoresist patterns in a plan view arranged close to each other at a predetermined distance in a matrix form,
The photoresist pattern is thermally melted to form a convex microlens pattern for transfer,
The three-dimensional shape of the transfer microlens pattern is transferred to the resin layer by dry etching the entire surface of the transfer microlens pattern and the resin layer, and the predetermined distance transferred to the resin layer is shortened to zero. , forming a microlens forming a plurality of rectangular shape in plan view of the micro lens unit side adjacent to each other are arranged in a matrix in contact. CF ₄ or oxygen and the formation method of claim 1, wherein the microlens performed using a mixed gas of CF ₄ as a process gas, by the entire dry etching of the transfer microlens pattern and the resin layer is a reactive ion etching apparatus. Method of forming the microlens microlens according to claim 1, wherein forming each photoelectric conversion element of the solid-state imaging device. The method for forming a microlens according to claim 3, wherein the solid-state imaging device is a CCD imaging device or a MOS type imaging device. The microlens forming method according to claim 1 microlens according to form each liquid crystal cell of a liquid crystal display device. Method of forming the microlens microlens according to claim 1 wherein formed on the intralayer lens.

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